In general, mobile communication systems have been developed for the purpose of providing communication services to a user while ensuring a user's mobility. With the rapid development of technologies, the mobile communication system has reached a stage of providing high-speed data communication services as well as voice communication. In recent years, a standardization operation has been in progress for Long Term Evolution-Advanced (LTE-A) in the 3GPP, as one of the next generation mobile communication systems. The LTE-A is a technology for implementing high-speed packet-based communication with a higher transmission rate than the data transmission rate currently available, aiming toward completion of standardization around late 2010.
As the 3GPP standards evolve, measures are under discussion to improve the communication speed in addition to the measures for optimizing the wireless network. In general, during initial deployment of the wireless network or when the wireless network is optimized, it is necessary for a base station or a base station control station to collect wireless environment information of their own cell coverage, which is referred to as a drive test. For a conventional drive test, there is inconvenience in carrying the measurement device in the car and repeating the measurement work which takes a long time be performed. The results of the above measurements are passing through the process of analysis and then used to set system parameters of each base station or base station controller. The drive test increases wireless network optimization costs and operational costs, and is time-consuming. Therefore, studies for minimizing the drive test and improving the analytical process and manual setting of the wireless environment are in progress under the name of Minimization of Drive Test (MDT). To this end, the UE, while measuring a radio channel instead of the drive test, transmits the measurement information of the radio channel to the base station periodically or immediately when a specific event occurs, or stores the measurement information of the radio channel for a predetermined time and then transmits to the base station. In the following, an operation of sending the radio channel measurement information measured and other additional information by the UE will be referred to as an MDT measurement information report. In this case, when the UE can communicate with the base station, the UE immediately transmits the result of the channel measurement to the base station, or, when the immediate report is not possible, the UE records the result and, when the communication becomes possible, then reports the recorded MDT measurement information to the base station. Then, the base station uses the MDT measurement information received from the UE in order to optimize the cell region.
FIG. 1 is a conceptual diagram for explaining an MDT performance. A conventional drive test 100 measures the state of a signal while the measurement equipment is carried in a vehicle, finding weak coverage, and walking around the service area. In the MDT, the UE 120 carries out the measurement in place of the drive test. A Network Monitoring System (NMS) 105 may indicate the MDT performance. At this time, necessary configuration information is provided to an Element Manager (EM) 110. The EM configures the MDT configuration and transmits the configured MDT to a base station (eNB) 115. The eNB 115 transmits the MDT configuration to the User Equipment (UE) 120 in step 125, and indicates the MDT performance. The UE 120 collects the MDT measurement information. The MDT measurement information may include not only the measurement information of the signal but also location and time information. The collected information is reported to the eNB 115 in step 130. The eNB 115 transmits the collected information to a Trace Collection Entity (TCE) 135. The Trace Collection Entity (TCE) 135 is a single server which collects MDT measurement information.